Concealed auxiliary cathode for figure illuminating discharge tube

ABSTRACT

A figure illuminating discharge tube having one common anode and a plurality of cathodes necessitated to illuminate one digit of the decimal number upon application of voltage to the anode and cathodes, which comprises means for effecting a glow discharge between the anode and any one of the cathodes with fairly quick efficiency as compared with the conventional tube of a similar character. To this end, an auxiliary cathode directly connected with a power source is provided for maintaining a golw discharge between such auxiliary cathode and the anode to emit ions within the tube.

United States Patent [191 Toda [ 51 Nov. 27, 1973 Inventor:

[73] Assignee: Sanyo Electric Co., Ltd., Osaka-fu,

Japan [22] Filed: June 9, 1971 [21] Appl. No.: 151,295

Hiroshi Toda, Tottori, Japan [30] Foreign Application Priority Data 3,418,509 12/1968 Frouws et a1. 313/109.5 3,508,101 4/1970 Tanji 313/1095 2,925,530 2/1960 Engelbart... 315/169 TV X 3,135,892 6/1964 Stenning 313/197 X Primary Examiner--Palmer C. Demeo Att0rneyStaas, Halsey and Gable 5 7 ABSTRACT A figure illuminating discharge tube having one common anode and a plurality of cathodes necessitated to illuminate one digit of the decimal number upon application of voltage to the anode and cathodes, which comprises means for effecting a glow discharge between the anode and any one of the cathodes with fairly quick efficiency as compared with the conventional tube of a similar character. To this end, an auxiliary cathode directly connected with a power source is provided for maintaining a glow discharge between such auxiliary cathode and the anode to emit ions within the tube.

14 Claims, 5 Drawing Figures July 8, 1970 Japan 45/68744 [52] US. Cl 313/109.5, 313/198, 313/210 [51] Int. Cl. H01j 61/66 [58] Field of Search 313/1095, 210, 198, 313/197; 315/169 TV [56] References Cited UNITED STATES PATENTS 3,617,793 11/1971 Matsushita et al 3l3/l09.5 2,936,389 5/1960 Frouws 2,632,128 3/1953 Hancock 313/210 X we: '2 H H CONCEALED AUXILIARY CATHODE FOR FIGURE ILLUMINATING DISCHARGE TUBE The present invention relates to a discharge tube and, more particularly, to a figure illuminating discharge tube wherein an improvement has been made to ensure the discharge of electricity to take place with fairly quick efficiency to illuminate an intended figure.

Heretofore, there has been proposed a discharge tube of the type having one anode and a plurality of cathodes arranged, for example, in the form of substantially square-cornered 8 shape so that these cathodes can be, during the discharge of electricity, selectively illuminated to indicate one digit of the decimal numbers zero through nine.

The discharge tube of the type above referred to is generally called as a glow discharge cold-cathode tube which has been largely employed in various electromechanical, electrical or electronic devices each having a figure indicator. In this discharge tube, the operation thereof depends upon the properties of a glow discharge. However, the glow discharge will not readily take place without the presence of ions within the tube at the moment voltage of the opposite polarities is respectively applied to the anode and cathodes, but will take place with a delay of time after the voltage has been applied thereto. By way of example, in a desk-top electronic calculator having a plurality of such discharge tubes, the delay of time will run from several millisecond to a few seconds after the calculator has been switched on. This delay of time may be negligible in view of the fact that the calculator is rarely operated at the same time as the calculator is switched on.

Particularly in connection with the electronic calculator, a convenient type of calculator has been recently contemplated as having a digital display system wherein the unnecessary O figures other than those included in the specific number indicated by the display system are substantially eliminated. For example, assuming that the calculator has the capability of counting up to eight significant digits and that the specific number indicated thereby is 9307", the four figures usually indicated to the left of the highest significant digit 9 of this specific number are preferably erased to avoid a possible confusion. To this end, the convenient type of the calculator has the digital display system designed such that only the figure illuminating discharge tubes associated with the serial positions of digits of the number 9307" are illuminated while no voltage necessary for effecting the glow discharge is applied to the remaining discharge tubes.

In the conventional electronic calculator having such a digital display system as hereinbefore described, there is a defect in that a delay of time will occur when a discharge tube leftwardly positioned next to the discharge tube indicating the digit 9" of the number 9307 is to be illuminated. The same reason as hereinbefore described may apply to this case, but the delay of time in this case will be critical to the operator of the calculator in the sense that, especially when the calculator is operated in rapid sequence, the operator will fail to ascertain the result currently indicated by the digital display system of the calculator.

Accordingly, an essential object of the present invention is to provide a figure illuminating discharge tube wherein means is provided for effecting the glow discharge with fairly quick efficiency to illuminate an intended figure.

Another object of the present invention is to provide a figure illuminating discharge tube wherein, in addition to a plurality ofcathodes arranged substantially in the form of square-cornered 8 shape so that these cathodes can be, during the discharge of electricity within said tube, selectively illuminated to indicate one digit of the decimal numbers 0 through 9, an auxiliary cathode is provided by which the glow discharge with fairly quick efficiency can be ensured.

A further object of the present invention is to provide a figure illuminating discharge tube adaptable in any digital display devices and which can be manufactured at low cost with the structure simplified without necessitating any complicated manufacturing process.

These and other objects and features of the present invention will become apparent from the following description taken by way of example in conjunction with preferred embodiment thereof with reference to the accompanying drawings, in which;

FIG. 1 is a front elevation of a figure illuminating discharge tube according to the present invention,

FIG. 2 is a cross section taken along the line IIII in FIG. 1,

FIG. 3 is a perspective view of an essential portion of the figure illuminating discharge tube of FIG. 1,

FIG. 4 is a schematic circuit diagram showing the figure illuminating discharge tube and an electric circuit associated with said discharge tube, taken for the purpose of illustrating the operation of the discharge tube according to the present invention, and

FIG. 5 is a similar view to FIG. 3, showing another embodiment of the present invention, wherein an auxiliary cathode is employed in the form of an elongated wire.

Referring now to FIGS. 1 and 2, the figure illuminating discharge tube constructed in accordance with the teachings of the present invention comprises a housing 10, preferably made of transparent glass material, the both ends of which are sealed in a known manner as indicated by 11 and 12, respectively, after the discharge tube has been completely assembled. This housing 10 is filled with an inert gas and accommodates therein an upstanding supporter 13 made of ceramic material, a lower end of which being rigidly mounted on a stem 14 which is in turn mounted on the inner surface of the sealed end 12 of the housing 10 and the other upper end thereof being formed into a reduced rectangular end 15 mounted with a plate member 16 preferably made of mica or ceramic. This plate member 16 has a diameter substantially equal to the inside diameter of the housing 10 so that the periphery of said member 16 is contacted to the inner surface of said'housing 10 for exactly positioning the supporter 13 within said housing 10. On the front surface of this supporter 13, a plurality of elongated recesses 18, a circular recess 19 and a cut-out portion 20 are formed. The elongated recesses 18 are arranged substantially in the form of square-cornered figure 8 about a central portion of the front surface for receiving therein the corresponding number of cathodes 21 which has been necessitated for selectively illuminating the decimal digits 0 through 9", the circular recess 19 being positioned adjacent to the lower right corner of the 8-shaped arrangement of the cathodes 21 while the cut-out portion 20 being, for example, positioned adjacent to the upper left corner of said 8-shaped arrangement of the cathodes particularly as shown in FIG. 3. The circular recess 19 is adapted to receive therein a cathode 22 whose illumination designates the presence of a decimal point, but this provision may be omitted and a separate discharge tube employed for this purpose in the digital display system of an electronic calculator. The cut-out portion 20 is adapted to receive therein an auxiliary cathode 23, the function of which will be mentioned later.

Each of all of the cathodes 21, 22 and 23 has one end situated in the corresponding recess 18 or 19 or the cut-out portion 20 and the other end extended through the supporter 13 and in turn connected with the adjacent end of a lead-in wire, generally indicated by 24, the other end of said lead-in wire 24 being extended to the outside of the housing through the stem 14 and then the sealed end 12. This other end of said lead-in wire 24 positioned outside the housing 10 is adapted to be connected with an external circuit such as a display control circuit, as shown by 25 in FIG. 4, for controlling the application of voltage to any one of the cathodes 21 and 22 in response to the operation of the relevant key (not shown) disposed on the keyboard of the calculator.

Mounted over the rectangular end of the supporter 13 within the housing 10 is a ring getter 26, the function of this getter 26 being well known in the art. Briefly, this getter is used for removing the last traces of air to attain a high vacuum in the tube. in the instance as shown, the getter is supported by a strip member 27 having one end rigidly connected with the outer periphery of the getter 26 and the other end rigidly connected or integrally formed with an anode plate 28 plated to the front surface of the supporter 13 by means of a known fitting method such as employing eyelets at 29, 30 and 31.

The anode plate 28, preferably made of nickel, is formed with a plurality of slots 32 arranged substantially in the same shape as the square-cornered 8 arrangement of the recesses 18 formed in the supporter 13 so that each of the cathodes 21 can be exposed to the outside through said slots 32. This anode plate 28 is also formed with a circular opening 33 substantially in register with the circular recess 19 so that the cathode 22 can be exposed to the outside through said opening 33, and connected at its lower end with the adjacent end ofa lead-in wire 24' having the other end extended to the outside of the housing 10 in the same manner and for the same purpose as that of the lead-in wire 24.

In the instance as shown in FIGS. 1 and 2, means for receiving therein the auxiliary cathode 23 is described as comprising the cut-out portion 20, as shown in FIG. 3, formed on the front surface of the supporter 13. However, this cut-out portion may be replaced by a transversely elongated recess 34 shown in FIG. 5 while the auxiliary cathode of relatively long length may be employed. If the auxiliary cathode is employed in the form of elongated wire with the employment of the elongated recess 34, the ions can be emitted during the discharge of electricity between the auxiliary cathode and the anode plate in a larger amount than in the foregoing embodiment shown in FIG. 1 through FIG. 3. However, in either case, when the anode plate 28 is plated to the front surface of the supporter 13 in such a manner as hereinbefore described, the cut-out portion 20 or the elongated recess 34 should be shielded from the field of view while the cavity formed thereby is communicated with the interior of the housing 10 to permit the migration of ions present in the discharge tube so long as voltage is applied to the anode plate 28 and the auxiliary cathode 23.

In any event, it is to be noted that the cutout portion 20 or the elongated recess 34 may be formed at any position on the front surface of the supporter 13 unless the auxiliary cathode 23 is exposed into the field of view. This is because the provision of the auxiliary cathode 23 is directed to maintain the discharge of electricity between the auxiliary cathode 23 and the anode plate 28 so long as the calculator is switched on and during a period in which no discharge of electricity is effected between the cathodes 21 and the anode plate 28. This means that, since the discharge of electricity continues between the auxiliary cathode 23 and the anode plate 28 so long as the calculator is switched on, the ions are emitted and, because of the presence of the ions, the cathodes 21 can be selectively illuminated readily upon application of voltage to the cathodes 21. For this reason, the auxiliary cathode 23 is not necessary to be watched by the operator of the calculator.

The operation of the discharge tube thus constructed in accordance with the present invention will be apparent from the foliowing description made with reference to FIG. 4.

Referring now to FIG. 4 in which a circuit diagram is schematically shown, each of the cathodes 21 and the cathode 22 are both connected through respective resistors with the display control circuit 25 which is in turn connected with a negative terminal of a power source 36. The auxiliary cathode 23 is directly connected with the negative terminal of the power source through a resistor and the anode plate 28 is connected with a positive terminal of the power source 36.

Accordingly, it will be clearly understood that the glow discharge will continue between the auxiliary cathode 23 and the anode plate 28 while the glow discharge between the cathodes 21 and the anode plate 28 will be selectively effected with fairly quick efficiency only when voltage of the power source is applied thereto through the display control circuit 25. Because of the presence of the ions emitted by the glow discharged between the auxiliary cathode 23 and the anode plate 28 as hereinbefore described, the glow discharge between the anode plate 28 and any one of the cathodes 21 can be readily effected upon application of voltage to the corresponding cathode through the display control circuit 25.

What is ciaimed is:

1. A figure illuminating discharge tube comprising:

a sealed envelope filled with gas at glow discharge pressure, said envelope having a transparent viewing surface therein;

a non-conductive cathode supporter mounted in the envelope, said cathode supporter having a cathode mounting surface that faces said viewing surface;

a plurality of exposed cathodes mounted in a figure defining configuration on said cathode mounting surface;

an auxiliary cathode mounted on said cathode mounting surface, said auxiliary cathode being in communication with said exposed cathodes;

a conductive anode mounted intermediate said cathode supporting surface and said viewing surface and spaced apart from the cathodes to permit selective electrical discharge between said anode and said cathodes,

electrical connectors affording selective energization of said cathodes and anode from the exterior of said tube envelope, and

said anode having a plurality of openings therein that mate with the exposed cathodes to render the selective discharge to each of the exposed cathodes visible through said viewing surface, and said anode concealing the auxiliary cathode from view through said viewing surface, thereby a discharge from the anode to the auxiliary cathode may be maintained continuously but concealed from view.

2. A figure illuminating discharge tube as recited in claim 1 further comprising:

a further exposed cathode mounted on said cathode mounting surface and positioned to define a decimal point location relative to said figure defining exposed cathodes,

an electrical connector affording selective energization of said further cathode from the exterior of said tube envelope, and

said anode having an opening therein mating with said further exposed cathode to render selective discharge thereto visible through said viewing surface.

3. A figure illuminating discharge tube comprising:

a sealed envelope filled with gas at glow discharge pressure, said envelope having a transparent viewing surface therein;

a non-conductive cathode supporter mounted in the envelope, said cathode supporter having a cathode mounting surface disposed towards said viewing surface and including a plurality of figure defining recesses therein;

a plurality of exposed cathodes mounted respectively in corresponding ones of said plurality of recesses;

a conductive anode mounted intermediate the cathode supporting surface and the viewing surface of said envelope, said anode having figure defining openings therein corresponding to the exposed cathodes to render said exposed cathodes visible through the viewing surface of the envelope;

an auxiliary cathode recess formed in the cathode supporter to be in communication with the interior of the tube envelope and the exposed cathodes and concealed from the viewing surface of the tube envelope by an opaque portion of the anode;

an auxiliary cathode mounted in said auxiliary cathode recess; and

means for electrically connecting the cathodes and anode to a suitable means for operating the tube,

whereby the auxiliary cathode may be maintained continuously in a conductive state in order to maintain the gas in the tube in an ionized condition at all times, thereby avoiding ignition delays in selectively discharging the exposed cathodes.

4. A discharge tube as recited in claim 3 wherein said anode is mounted in superposed relationship on said cathode supporting surface.

5. A discharge tube as recited in claim 4, wherein the auxiliary cathode recess is formed as a cut-out portion of said cathode supporting surface extending inwardly from an edge thereof to afford said communication.

6. A discharge tube as recited in claim 5 wherein said auxiliary cathode comprises a circular electrode;

7. A discharge tube as recited in claim 4, wherein the auxiliary cathode recess is formed as an elongated recess extending the entire width of the cathode supporting surface; and the auxiliary cathode comprises a wire that extends longitudinally along the recess.

8. An illuminating discharge tube as recited in claim 3 further comprising:

a further exposed cathode mounted on said cathode mounting surface and positioned to define a decimal point location relative to said figure defining exposed cathodes an electrical connector affording selective energization of said further cathode from the exterior of said tube envelope, and

said anode having an opening therein mating with said further exposed cathode to render selective discharge thereto visible through said viewing surface. I

9. In a figure illuminating glow discharge tube comprising a sealed envelope having a transparent viewing surface and being filled with gas at glow discharge pressure, a cathode supporter having a cathode supporting surface with a plurality of figure defining recesses therein, exposed cathodes mounted in said recesses, an anode mounted on the cathode supporting surface and having a plurality of figure defining openings therein that mate with the figure defining recesses in the cathode supporter to render the latter visible through said viewing surface, the improvement comprising:

an auxiliary cathode recess in said cathode supporting surface and in communication with the interior of the tube envelope and the exposed cathodes;

an auxiliary cathode mounted in said auxiliary cathode recess, and

said anode concealing said auxiliary cathode from view through said viewing surface.

10. In a figure illuminating device as recited in claim 9 further including:

a power source and means for selectively connecting the power source to the exposed cathodes so as to permit selective discharge between said anode and said exposed cathodes in accordance with desired figures to be displayed, the improvement comprismg:

means connecting said power source to said auxiliary cathode so as to maintain a continuous discharge to said auxiliary cathode.

11. An illuminating discharge tube comprising:

a sealed envelope filled with gas at glow discharge pressure, said envelope having a transparent viewing surface therein;

a non-conductive cathode supporter mounted in the envelope, said cathode supporter having a cathode mounting surface that faces said viewing surface;

at least one exposed cathode mounted on said cathode mounting surface;

an auxiliary cathode mounted on said cathode mounting surface, said auxiliary cathode being in communication with said exposed cathode;

a conductive anode mounted intermediate said cathode supporting surface and said viewing surface and spaced apart from the exposed cathode to permit selective electrical discharge between said anode and said cathode,

means affording selective energization of said cathode and anode from the exterior of said tube envelope, and

said anode having an opening therein that mates with the exposed cathode to render the selective discharge to the exposed cathode visible through said viewing surface, and said anode concealing the auxiliary cathode from view through said viewing surface, whereby a discharge from the anode to the auxiliary cathode may be maintained continuously but concealed from view.

12. An illuminating discharge tube as recited in claim 11 for displaying a decimal point in a line of figures displayed by associated figure display devices wherein said one exposed cathode is positioned on said cathode supporter so as to define a decimal point position in said line of figures 13. An illuminating discharge tube as recited in claim 11 wherein:

said cathode supporter includes a recess therein for receiving said exposed cathode and an auxiliary recess for receiving therein said auxiliary cathode and being in communication with the interior of the tube envelope and the exposed cathodes.

14. An illuminating discharge tube as recited in claim 11 wherein there is further provided:

thereto visible through said viewing surface. 

1. A figure illuminating discharge tube comprising: a sealed envelope filled with gas at glow discharge pressure, said envelope having a transparent viewing surface therein; a non-conductive cathode supporter mounted in the envelope, said cathode supporter having a cathode mounting surface that faces said viewing surface; a plurality of exposed cathodes mounted in a figure defining configuration on said cathode mounting surface; an auxiliary cathode mounted on said cathode mounting surface, said auxiliary cathode being in communication with said exposed cathodes; a conductive anode mounted intermediate said cathode supporting surface and said viewing surface and spaced apart from the cathodes to permit selective electrical discharge between said anode and said cathodes, electrical connectors affording selective energization of said cathodes and anode from the exterior of said tube envelope, and said anode having a plurality of openings therein that mate with the exposed cathodes to render the selective discharge to each of the exposed cathodes visible through said viewing surface, and said anode concealing the auxiliary cathode from view through said viewing surface, thereby a discharge from the anode to the auxiliary cathode may be maintained continuously but concealed from view.
 2. A figure illuminating discharge tube as recited in claim 1 further comprising: a further exposed cathode mounted on said cathode mounting surface and positioned to define a decimal point location relative to said figure defining exposed cathodes, an electrical connector affording selectivE energization of said further cathode from the exterior of said tube envelope, and said anode having an opening therein mating with said further exposed cathode to render selective discharge thereto visible through said viewing surface.
 3. A figure illuminating discharge tube comprising: a sealed envelope filled with gas at glow discharge pressure, said envelope having a transparent viewing surface therein; a non-conductive cathode supporter mounted in the envelope, said cathode supporter having a cathode mounting surface disposed towards said viewing surface and including a plurality of figure defining recesses therein; a plurality of exposed cathodes mounted respectively in corresponding ones of said plurality of recesses; a conductive anode mounted intermediate the cathode supporting surface and the viewing surface of said envelope, said anode having figure defining openings therein corresponding to the exposed cathodes to render said exposed cathodes visible through the viewing surface of the envelope; an auxiliary cathode recess formed in the cathode supporter to be in communication with the interior of the tube envelope and the exposed cathodes and concealed from the viewing surface of the tube envelope by an opaque portion of the anode; an auxiliary cathode mounted in said auxiliary cathode recess; and means for electrically connecting the cathodes and anode to a suitable means for operating the tube, whereby the auxiliary cathode may be maintained continuously in a conductive state in order to maintain the gas in the tube in an ionized condition at all times, thereby avoiding ignition delays in selectively discharging the exposed cathodes.
 4. A discharge tube as recited in claim 3 wherein said anode is mounted in superposed relationship on said cathode supporting surface.
 5. A discharge tube as recited in claim 4, wherein the auxiliary cathode recess is formed as a cut-out portion of said cathode supporting surface extending inwardly from an edge thereof to afford said communication.
 6. A discharge tube as recited in claim 5 wherein said auxiliary cathode comprises a circular electrode.
 7. A discharge tube as recited in claim 4, wherein the auxiliary cathode recess is formed as an elongated recess extending the entire width of the cathode supporting surface; and the auxiliary cathode comprises a wire that extends longitudinally along the recess.
 8. An illuminating discharge tube as recited in claim 3 further comprising: a further exposed cathode mounted on said cathode mounting surface and positioned to define a decimal point location relative to said figure defining exposed cathodes an electrical connector affording selective energization of said further cathode from the exterior of said tube envelope, and said anode having an opening therein mating with said further exposed cathode to render selective discharge thereto visible through said viewing surface.
 9. In a figure illuminating glow discharge tube comprising a sealed envelope having a transparent viewing surface and being filled with gas at glow discharge pressure, a cathode supporter having a cathode supporting surface with a plurality of figure defining recesses therein, exposed cathodes mounted in said recesses, an anode mounted on the cathode supporting surface and having a plurality of figure defining openings therein that mate with the figure defining recesses in the cathode supporter to render the latter visible through said viewing surface, the improvement comprising: an auxiliary cathode recess in said cathode supporting surface and in communication with the interior of the tube envelope and the exposed cathodes; an auxiliary cathode mounted in said auxiliary cathode recess, and said anode concealing said auxiliary cathode from view through said viewing surface.
 10. In a figure illuminating device as recited in claim 9 further including: a power source and means for selectively connecting the poweR source to the exposed cathodes so as to permit selective discharge between said anode and said exposed cathodes in accordance with desired figures to be displayed, the improvement comprising: means connecting said power source to said auxiliary cathode so as to maintain a continuous discharge to said auxiliary cathode.
 11. An illuminating discharge tube comprising: a sealed envelope filled with gas at glow discharge pressure, said envelope having a transparent viewing surface therein; a non-conductive cathode supporter mounted in the envelope, said cathode supporter having a cathode mounting surface that faces said viewing surface; at least one exposed cathode mounted on said cathode mounting surface; an auxiliary cathode mounted on said cathode mounting surface, said auxiliary cathode being in communication with said exposed cathode; a conductive anode mounted intermediate said cathode supporting surface and said viewing surface and spaced apart from the exposed cathode to permit selective electrical discharge between said anode and said cathode, means affording selective energization of said cathode and anode from the exterior of said tube envelope, and said anode having an opening therein that mates with the exposed cathode to render the selective discharge to the exposed cathode visible through said viewing surface, and said anode concealing the auxiliary cathode from view through said viewing surface, whereby a discharge from the anode to the auxiliary cathode may be maintained continuously but concealed from view.
 12. An illuminating discharge tube as recited in claim 11 for displaying a decimal point in a line of figures displayed by associated figure display devices wherein said one exposed cathode is positioned on said cathode supporter so as to define a decimal point position in said line of figures.
 13. An illuminating discharge tube as recited in claim 11 wherein: said cathode supporter includes a recess therein for receiving said exposed cathode and an auxiliary recess for receiving therein said auxiliary cathode and being in communication with the interior of the tube envelope and the exposed cathodes.
 14. An illuminating discharge tube as recited in claim 11 wherein there is further provided: a plurality of exposed cathodes in addition to said one exposed cathode and mounted in a figure defining configuration on said cathode mounting surface and in communication with said auxiliary cathode, said one exposed cathode being mounted relatively to said plurality of exposed cathodes so as to define a decimal point position, said energization means affords selective energization of said plurality of exposed cathodes from the exterior of said tube envelope, and said anode has a plurality of further openings therein respectively mating with said plurality of further exposed cathodes to render selective discharge thereto visible through said viewing surface. 